JPH0293603A - Optical transmission body made of synthetic resin - Google Patents

Abstract

PURPOSE:To improve radiation without deteriorating transmission characteristics by copolymerizing org. carboxylic acid and the lead salt of the org. carboxylic acid with an optical fiber consisting of a PMMA system. CONSTITUTION:The core is constituted of the copolymer of the monomer compsns. of the org. carboxylic acid, the lead salt thereof and methyl methacrylate. The polymer components forming the core area 60 to 98wt.% content of methacrylic acid, 1 to 40wt.% content of the org. carboxylic acid and 0.1 to 30wt.% content of the lead salt of the org. carboxylic acid. The lead salt of the org. carboxylic acid has excellent transparency and radiation resistance and, therefore, the dispersibility of the lead ions in a resin is improved and the radiation resistance characteristics are uniformized and stabilized if the org. carboxylic acid is copolymerized in combination at the time of copolymerizing this lead salt.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application 1] The present invention relates to a synthetic resin optical transmission body, that is, a plastic optical fiber, and particularly to a plastic optical fiber having excellent radiation resistance.

[Conventional technology 1] Plastic optical fibers have the disadvantage of higher transmission loss than silica-based optical fibers, but they have a thick fiber diameter (usually 0.1 to 3.0 mm), are flexible, and have excellent bending resistance. It has the advantages of being resistant to bending impact and easy to perform connection work such as axis alignment, and its practical use as a transmitter for optical transmission over short distances such as day links and sensors is rapidly progressing. be.

As one of the application fields for warping, serious consideration is being given to using it in place of silica-based optical fibers, which have traditionally had many problems in radiation atmospheres such as monitoring and controlling equipment in nuclear reactors.

[Problems to be Solved by the Invention] Plastic optical fibers that have been commercially available and put into practical use so far include so-called PMMA, which uses polymethyl methacrylate for the core and fluorinated (meth)acrylate copolymer resin for the cladding. system optical fiber is the mainstream.

However, this PMMA optical fiber cannot necessarily be said to have excellent radiation resistance, and as the field of application is expanded to include the above-mentioned radiation atmosphere, there is an increasing demand for improvement.

In view of the above-mentioned circumstances, an object of the present invention is to provide a plastic optical fiber with excellent radiation resistance that can be used even in a radiation atmosphere.

[Means for Solving the Problems] The present invention uses the same base material as the PMMA system described above as the base material constituting the core and cladding, but adds organic carboxylic acid and organic carboxylic acid lead salt to these materials. It is a copolymerized product, which dramatically improves radiation resistance without deteriorating transmission characteristics.

[Function] Organic carboxylic acid lead salts have excellent transparency as well as excellent radiation resistance. When this is copolymerized with an organic carboxylic acid, the dispersion of lead ions in the resin can be improved and the radiation resistance properties can be made more uniform and stable.

[Example 1 The present invention will be sequentially explained below with reference to Examples.

In the present invention, the core is constituted by a copolymer of a monomer composition consisting of an organic carboxylic acid, its lead salt, and methyl methacrylate.

Among the polymer components forming the core, methyl methacrylate forms the basis of the physical properties of the resin, such as transparency, weather resistance, and mechanical strength. Therefore, it is desirable that the content of this component is 60% by weight or more, and if it is less than this, the basic properties will not be maintained satisfactorily. Furthermore, if the content of this component exceeds 98% by weight, the improvement in radiation resistance will be insufficient, which is not preferable.

Further, a component consisting of an organic carboxylic acid lead salt is a component that is present in the copolymer and improves radiation resistance. Furthermore, this component is a component that contributes to the compatibility of the copolymer, and is involved in the transparency and reactivity of the copolymer.

Therefore, if this component is less than 0.1% by weight, the improvement in transparency and radiation resistance will be insufficient, which is undesirable.If this component is more than 30ffi, the flowability during melting will deteriorate, resulting in poor moldability and optical properties. There is also a tendency for the physical properties to decline. 30% by weight especially if you dislike such a tendency.
It is desirable to keep it below.

In addition, although the component consisting of organic carboxylic acid itself has a small effect on improving the radiation resistance of the obtained copolymer,
Increases compatibility with heat resistance improving components, namely organic carboxylic acid metal salts and methyl methacrylate, and indirectly improves radiation resistance.
This can contribute to the improvement of a. This component has a large effect on the mechanical properties, optical properties, and moldability of the copolymer. Therefore, the content of this organic carboxylic acid component is preferably kept in the range of 1 to 40% by weight. If the amount is more or less than that, there is a risk that the optical properties of the obtained core material copolymer will be deteriorated.

This organic carboxylic acid component is greatly involved in the dispersion state of lead <n> ions in the resin, and the present inventors have discovered that acrylic acid or methacrylic acid and the general formula (1) shown below
, (2) or (3), it was confirmed through experiments that the dispersion state of button (n) ions could be improved.

Rr-C-0)1 (In the formula, R1 is an unsaturated hydrocarbon group having 6 to 20 carbon atoms, or an unsaturated hydrocarbon including an alicyclic hydrocarbon.) (In the formula, R2 is hydrogen or carbon R3 is an unsaturated hydrocarbon group having 2 to 10 carbon atoms, and R3 is a hydrocarbon residue having 1 to 10 carbon atoms.

) (wherein, R4 is hydrogen or an alkyl group having 1 to 3 carbon atoms,
R5 is a hydrocarbon residue having 1 to 10 carbon atoms, and n is an integer of 1 to 10. ) It is necessary to maintain a low refractive index. As such a rad material, in the present invention, a copolymer of a monoplane composition consisting of an organic carboxylic acid, its lead salt and a fluorinated (meth)acrylate is used.

As a component of the cladding material polymer of the present invention, the fluorinated (meth)acrylic acid ester provides basic physical properties of the resin such as low refractive index, transparency, and weather resistance. As the fluorinated (meth)acrylic ester, those shown in the following general formulas (4) and (5) can be considered.

In the present invention, it is desirable to select and use at least one type from the above organic carboxylic acids.

On the other hand, in the present invention, it is desirable that the cladding has excellent radiation resistance like the core, and in order to allow the core to transmit light, it is more flexible than the core (where X is F or H, and Y is CH3 or H, n+ is an integer of 2 to 10, and 1 is an integer of 1 to 6.) The component consisting of organic carboxylic acid lead salt in the clad copolymer component was included as the core component. Like the organic carboxylic acid lead salt, it is a component that improves radiation resistance, and in the same sense as the core, it is desirable to use it in the range of 0.1% to 30% by weight in the cladding material component.

Similarly, as the organic carboxylic acid as the cladding material copolymer component, it is desirable to use the organic carboxylic acid proposed for the core material, and the amount used is also preferably in the range of 1 to 40% by weight. .

In addition, the clad copolymer component used in the present invention only needs to have a sufficiently low refractive index as a clad material, and includes methacrylic acid esters such as methyl methacrylate, ethyl acrylate, etc. There is no problem in including a monomer such as acrylic ester in an amount of 50% by weight or less, if necessary.

In the present invention, a soluble polymerization initiator is used to polymerize the copolymer of the core material and the cladding material. Examples of the polymerization initiator used in the present invention include benzoyl peroxide, lauroyl peroxide, and dicystidyl peroxide. Peroxides such as luperoxide, 2,2-1 azobisisobutyronitrile, 2,2-1azobis-(2,4
-dimethylvaleronitrile), 2.2--azobis-(
Known radical initiators such as azobis-based initiators such as 2.4-dimethyl-4-methoxy-valeronitrile can be used.

Further, in the polymerization system, both -functional and polyfunctional chain transfer agents including a chain transfer agent can be used to improve moldability and the like. Typical examples include n-butylmercaptan, sec-butylmercaptan, n-dodecylmercaptan, t-dodecylmercaptan, laurylmercaptan, mercaptoacetic acid, and the like.

The amounts of the polymerization initiator and chain transfer agent contribute to the molecular weight of the copolymer and are determined from the balance between moldability and heat resistance6.
The polymerization initiator is used in an amount of about 0.01 to 10% by weight, preferably 0.1 to 5% by weight of the total monomers.

To produce a copolymer, the copolymerization component mixture is
Bulk polymerization is carried out at ~180°C.

Alternatively, solution polymerization may be performed in which the copolymerization mixture is subjected to a polymerization reaction in a suitable solvent. Typical solvents include acetone, ethyl #acid, n-butyl acetate, chloroporum, carbon tetrachloride, benzene, and methanol. , ethanol, and tetrahydrofuran. Furthermore, suspension polymerization may be carried out in which polymerization is carried out in an aqueous medium containing a suspending and dispersing agent.

Example 1゜Methyl methacrylate 1000tr, methacrylic acid 30g
, 30 g of cicaprolactone acrylate, 20 g of dimethacrylic acid SH, 6 g of n-butyl mercaptan, 2.
2-5 g of azobisisobutyronitrile was injected into a cell formed by glass plates facing each other at 5-space intervals with a Teflon gasket interposed therebetween, and immersed in warm water at 65°C for 4 hours to cause a polymerization reaction. Ta. Then 120℃ for 2 hours, 15
It was cured in an electric constant temperature bath at 0°C for 2 hours. The obtained resin plate was crushed and used as a core material. 2,2.2-) Lifluoroethyl methacrylate 1000g, methacrylic acid 30
f, cicaprolactone acrylate-1.30t, lead dimethacrylate 20z, n-butylmercaptan 3g, 2.2
- 5 g of azobisisobutyronitrile was reacted in the same manner and under the same conditions as the core material to obtain a cladding material.

The obtained core material and cladding material were used in a composite spinneret to form a core with a diameter of 1.0 and a cladding with a diameter of 1.0. '10. Two fin fibers were heated and melt spun. The obtained optical fiber 5m is 1
Irradiation was carried out for 50 hours with cobalt gamma rays at 0.4 rad/hour. 660 nm L E of the fiber after irradiation
When the amount of transmitted light with D light was measured, it had a light amount retention rate of 95% or more compared to that before irradiation.

Example 2゜Metal methacrylate 1000z, acrylic acid 50g,
Polymerization was carried out using 20 tr of cinnamic acid, lead diacrylate SOW, 6 g of n-butylmercaptan, and 5 g of 2.2'-azobisisobutyronitrile in the same manner and under the same conditions as in Example 1 to obtain a core material.

2.2.2-Trifluoroethyl methacrylate 600
g, methyl methacrylate 400tr, methacrylic acid 50
Polymerization was proceeded using the same method and conditions as in Example 1 to obtain a cladding material.

The obtained core material and cladding material copolymer were prepared in the same manner as in Example 1, with a core diameter of 1.0+wm and a cladding thickness of 0.
．． 2n+n fibers were created.

5 m of the obtained optical fiber was irradiated with cobalt gamma rays at 104 rad/hour for 50 hours. When the amount of transmitted light of the 660 nm LED light of the fiber after irradiation was measured, it had a light amount retention rate of 95% or more compared to that before irradiation.

Comparative Example 1 A 5 m optical fiber (core diameter 1.0 mm, cladding thickness 0.1 mm) having a core of polymethyl methacrylate and a cladding of vinylidene fluoride-tetrafluoroethylene copolymer was prepared under the same conditions as in Example 1. γ-ray irradiation was performed. When looking at the light transmission performance of the obtained plastic optical fiber for 660 nm LED light, the light intensity retention rate was 80% or less compared to that of the unirradiated one, confirming the excellent radiation resistance of the optical fiber according to the present invention. .

[Effects of the Invention] As described above, according to the present invention, a plastic optical fiber with extremely high radiation resistance can be obtained, and optical measurement and optical transmission systems can be introduced into equipment surrounding nuclear reactors. Its industrial value is extremely large, as it makes it easier to use.

Agent: Patent Attorney Fujio Sato

Claims (3)

[Claims] (1) A synthetic resin optical transmission body consisting of a core and a cladding provided on its outer periphery, in which the core is made of a copolymer of a monomer composition consisting of an organic carboxylic acid, its lead salt, and methyl methacrylate. . (2) The content of methyl methacrylate as a monomer constituting the copolymer that is the core material is 60 to 98% by weight, the content of organic carboxylic acid is 1 to 40% by weight, and the content of organic carboxylic acid lead salt is 60 to 98% by weight. The synthetic resin light transmitting body according to claim 1, wherein the content is 0.1 to 30% by weight. (3) The synthetic resin optical transmitter according to claim 1 or 2, wherein the cladding material is a copolymer of a monomer composition consisting of an organic carboxylic acid, its lead salt, and a fluorinated (meth)acrylate.